Improvement in the crystal quality of ZnSe films on Si(111) substrates with a nitrogen surface treatment

We have achieved a significant improvement in the crystal quality of ZnSe f ilms grown by pulsed molecular beam epitaxy (MBE) on Si(lll) by irradiating the substrates with a plasma of nitrogen (N-plasma) prior to the depositio n. Reflection high-energy electron diffraction (RHEED) patterns during the pulsed MBE growth on the N-plasma-treated Si surface showed very well defin ed streaks with a twofold reconstruction indicating an atomically flat surf ace. In sharp contrast spotty RHEED patterns with a diffuse background were observed during the initial stages of the conventional MBE growth of ZnSe on untreated substrates, indicating an initial three-dimensional growth mod e. Atomic force microscopy confirmed a smoother surface for the samples gro wn on the N-plasma-treated Si substrates. Moreover, transmission electron m icroscopy revealed a decrease in the density of crystal defects in the ZnSe epilayers by the use of the N-plasma treatment. (C) 2000 Elsevier Science S.A. All rights reserved.